Houdini's "explode node" in Animation Nodes
If I understand you correct, what you essentially need is a way to store the initial transformation of objects.

Fortunally Animation Nodes (AN) has an in-build system for that. It is called the ID-Key system (the name comes from the fact that it can theoretically work with all types of ID-Objects in Blender)

Using it is relatively simple - if you know about it:


Select all objects whose transformation you want to save in an ID Key.
Go to the AN tab in the toolshelf of the 3D View and open the ID Keys panel. There you have to click the "From Current Transforms" button. This will store the location, rotation and scale of each selected object in custom properties. You can also see them in the object settings.

Open the node editor, insert a Object ID Key node, click Choose Key and select Initial Transformation. Now you can get the initial location, rotation, etc of the object you have as input. The Initial Transformation of an object does not change unless you press that button again.



The ID-Key system is a generic solution to the underlying problem of storing values per object that are not changed by your nodes. 

The same system is used by the Separate Text Object node. If you look at the template, it also uses the Object ID Key node. Also it does not only store the initial transformation of a letter but also the inital text-value.